Transition metal-catalyzed cross-coupling reactions have received significant attention, and become extremely versatile protocols in organic synthesis for the connection of carbon-carbon and/or carbon-heteroatom bonds. Particularly, various kinds of well-known coupling reactions, such as Suzuki-Miyaura reaction for the construction of diversified biaryls, Buchwald-Hartwig amination reaction for the construction of amines, Heck reaction for the construction of olefins or dienes, have numerous applications in pharmaceutical, material, and agricultural chemistry in the past few decades. The structure of ligands has been recognized as being able to significantly affect the efficiency of cross-coupling reactions. Thus, the strategic design of ligands with appropriate steric and electronic diversity, and streamlined synthetic protocol is crucial in dealing with problematic and specific substrates in this area.
The lore in this field is that the palladium catalysts contain sterically bulky and electron-rich phosphines that are effective for aromatic carbon-carbon and carbon-nitrogen bond-forming processes from aryl chlorides. Noteworthy, Beller (Zapf. A.; Sundermeier, M.; Jackstell, R.; Beller, M.; Riermeier, T; Monsees, A.; Dingerdissen, U., WO 2004/101581 A2), Buchwald (Buchwald, S. L.; Fors, B. P.; Surry, D. S., WO 2009/076622A2; Buchwald, S. L.; Old, D. W.; Wolfe, J. P.: Palucki, M.; Kamikawa, K., U.S. Pat. No. 6,307,087 B1), Fu, Hartwig and other groups highly contribute to the phosphine ligand design and synthesis.